1. Field of the Invention
The present invention relates to a V-type engine, an outboard motor powered by the V-type engine, and a vessel propelled by the outboard motor.
2. Description of the Related Art
A vessel described in each of Japanese Unexamined Patent Publication No. 2008-31868, Japanese Unexamined Patent Publication No. 2008-31897, and Japanese Unexamined Patent Publication No. 2008-31898 includes an outboard motor powered by a V-type eight-cylinder engine. Each engine is equipped with an in-bank exhaust system that discharges exhaust gas to an inner side of two cylinder banks.
The exhaust device of Japanese Unexamined Patent Publication No. 2008-31868 includes eight upstream exhaust pipes connected to the two cylinder banks, four midstream exhaust pipes, by which the eight upstream exhaust pipes are merged into four pipes, and a single downstream exhaust pipe, by which the four midstream exhaust pipes are merged into a single pipe.
The exhaust device of Japanese Unexamined Patent Publication No. 2008-31897 includes eight upstream exhaust pipes connected to the two cylinder banks, four midstream exhaust pipes, by which the eight upstream exhaust pipes are merged into four pipes, and two downstream exhaust pipes, by which the four midstream exhaust pipes are merged into two pipes.
As with the device of Japanese Unexamined Patent Publication No. 2008-31897, the exhaust device of Japanese Unexamined Patent Publication No. 2008-31898 includes eight upstream exhaust pipes connected to the two cylinder banks, four midstream exhaust pipes, by which the eight upstream exhaust pipes are merged into four pipes, and two downstream exhaust pipes, by which the four midstream exhaust pipes are merged into two pipes.
With these conventional vessels, each midstream exhaust pipe of the exhaust device is connected to an upstream exhaust pipe connected to one of the cylinder banks and connected to an upstream exhaust pipe connected to the other cylinder bank. The two upstream exhaust pipes branching from the midstream exhaust pipe in common are connected to two cylinders that differ in ignition timing. It is described that exhaust interference, which lowers the engine output, is thus prevented.
With an outboard motor, the restrictions of the space in which the engine is disposed are more severe than those of an automobile and it is thus preferable for the engine to be compact. However, with the V-type engine equipped with the in-bank exhaust system, the plurality of exhaust pipes meander in the width direction of the engine and the width of the exhaust pipes as a whole is wide. The engine is thus large in the width direction.